tanhl

       #include <math.h>

       double tanh(double x);
       float tanhf(float x);
       long double tanhl(long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       tanhf(), tanhl():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

DESCRIPTION
       These functions return the hyperbolic tangent of x,  which  is  defined
       mathematically as:

           tanh(x) = sinh(x) / cosh(x)

RETURN VALUE
       On success, these functions return the hyperbolic tangent of x.

       If x is a NaN, a NaN is returned.

       If x is +0 (-0), +0 (-0) is returned.

       If x is positive infinity (negative infinity), +1 (-1) is returned.

ERRORS
       No errors occur.

ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       +-------------------------+---------------+---------+
       |Interface                | Attribute     | Value   |
       +-------------------------+---------------+---------+
       |tanh(), tanhf(), tanhl() | Thread safety | MT-Safe |
       +-------------------------+---------------+---------+
CONFORMING TO
       C99, POSIX.1-2001, POSIX.1-2008.

       The variant returning double also conforms to SVr4, 4.3BSD, C89.

SEE ALSO
       acosh(3), asinh(3), atanh(3), cosh(3), ctanh(3), sinh(3)

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